Reference for Nedarim 137:1
שמע אביה והפר לה ולא הספיק הבעל לשמוע עד שמת חוזר האב ומפר חלקו של בעל א"ר נתן הן הן דברי ב"ש ב"ה אומרים אין יכול להפר
If the father heard and annulled it, and the husband died before he managed to hear of it, the father can again annul the husband's portion. R. Nathan said; That is the view of Beth Shammai; but Beth Hillel maintain: He cannot annul it [a second time]. This proves that according to Beth Shammai, he cuts it apart, whilst in the view of Beth Hillel he weakens it.<span class="x" onmousemove="('comment',' Hence, according to Beth Shammai, when the father annulled it, the husband's portion remains, as it were, intact in all its stringency. The husband's right to annul the other half is sufficiently tangible, since that half is as stringent in itself as the whole, to be transmitted to the father. But in the views of Beth Hillel annulment by the father, as by the husband, merely weakens it; hence the husband's right to wipe off entirely a prohibition that is already weakened is too intangible to be transmitted to the father. — But in the first clause, where without the father having annulled his share, the husband annuls it and then dies, since the father can annul his own share he can annul too the weakened share of the husband (Asheri). ');"><sup>1</sup></span>